Drug screening refers to a process to screen substances useful as drugs from various kinds of naturally occurring or artificially synthesized substances and drug candidates by reacting the substances with cells and observing changes of the cells induced by the substances. A great deal of research is currently being conducted around the world on drug screening for the purpose of finding anticancer drugs capable of selectively destroying cancer cells. Recent remarkable developments in genomics, proteomics, and combinatorial chemistry have led to a marked increase in the number of various kinds of drug candidates. However, all drug candidates are difficult to handle by existing drug screening that has been performed on well-plates. Under such circumstances, microfluidics has received considerable attention due to the possibility of greatly reducing the quantity of samples used at one time.
Microcapsules and related technologies thereof are increasingly investigated in various fields, including drug delivery based on the principle that capsules are broken or expand under particular ambient environmental conditions (e.g., temperature and pH) to release substances (e.g., drugs) contained therein to the outside and allow the released substances to react with surrounding substances. Such microcapsule-related technologies are not substantially applied to the field of drug screening. The greatest reason for this is because numerous drug candidates cannot be perfectly handled due to the limited number of codes that can be engraved on microcapsules.
Most current microarray-based drug screening techniques employ spotting drugs on the surface of array chips using suitable equipment, such as inkjet printers, and recognizing coordinates of drug arrays spotted on the chips as codes to match the codes with the drugs. These techniques have an advantage in that small quantities of samples can be used but require the use of expensive equipment. Another troublesome problem associated with an increase in the number of drugs is frequent exchange of the drugs with new ones in the toners of printers.